/**
 * Created by SLICE_30_K on 2017/5/22.
 *
 * 支持一般Base64的编码和解码
 * 支持符合RFC_4648标准中"URL and Filename Safe Alphabet"的URL安全Base64编解码
 * 支持中文字符的编解码(Unicode编码)
 */
 ;(function (root, factory) {
  if (typeof exports === "object") {
      // CommonJS
      module.exports = exports = factory();
  }
  else if (typeof define === "function" && define.amd) {
      // AMD
      define(factory);
  }
  else {
      // Global (browser)
      window.BASE64 = factory();
  }
}(this, function () {
  var BASE64_MAPPING = [
      'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H',
      'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P',
      'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X',
      'Y', 'Z', 'a', 'b', 'c', 'd', 'e', 'f',
      'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n',
      'o', 'p', 'q', 'r', 's', 't', 'u', 'v',
      'w', 'x', 'y', 'z', '0', '1', '2', '3',
      '4', '5', '6', '7', '8', '9', '+', '/'
  ];
  var URLSAFE_BASE64_MAPPING = [
      'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H',
      'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P',
      'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X',
      'Y', 'Z', 'a', 'b', 'c', 'd', 'e', 'f',
      'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n',
      'o', 'p', 'q', 'r', 's', 't', 'u', 'v',
      'w', 'x', 'y', 'z', '0', '1', '2', '3',
      '4', '5', '6', '7', '8', '9', '-', '_'
  ];

  var _toBinary = function (ascii) {
      var binary = [];
      while (ascii > 0) {
          var b = ascii % 2;
          ascii = Math.floor(ascii / 2);
          binary.push(b);
      }
      binary.reverse();
      return binary;
  };

  var _toDecimal = function (binary) {
      var dec = 0;
      var p = 0;
      for (var i = binary.length - 1; i >= 0; --i) {
          var b = binary[i];
          if (b == 1) {
              dec += Math.pow(2, p);
          }
          ++p;
      }
      return dec;
  };

  var _toUTF8Binary = function (c, binaryArray) {
      var mustLen = (8 - (c + 1)) + ((c - 1) * 6);
      var fatLen = binaryArray.length;
      var diff = mustLen - fatLen;
      while (--diff >= 0) {
          binaryArray.unshift(0);
      }
      var binary = [];
      var _c = c;
      while (--_c >= 0) {
          binary.push(1);
      }
      binary.push(0);
      var i = 0, len = 8 - (c + 1);
      for (; i < len; ++i) {
          binary.push(binaryArray[i]);
      }

      for (var j = 0; j < c - 1; ++j) {
          binary.push(1);
          binary.push(0);
          var sum = 6;
          while (--sum >= 0) {
              binary.push(binaryArray[i++]);
          }
      }
      return binary;
  };

  var _toBinaryArray = function (str) {
      var binaryArray = [];
      for (var i = 0, len = str.length; i < len; ++i) {
          var unicode = str.charCodeAt(i);
          var _tmpBinary = _toBinary(unicode);
          if (unicode < 0x80) {
              var _tmpdiff = 8 - _tmpBinary.length;
              while (--_tmpdiff >= 0) {
                  _tmpBinary.unshift(0);
              }
              binaryArray = binaryArray.concat(_tmpBinary);
          } else if (unicode >= 0x80 && unicode <= 0x7FF) {
              binaryArray = binaryArray.concat(_toUTF8Binary(2, _tmpBinary));
          } else if (unicode >= 0x800 && unicode <= 0xFFFF) {//UTF-8 3byte
              binaryArray = binaryArray.concat(_toUTF8Binary(3, _tmpBinary));
          } else if (unicode >= 0x10000 && unicode <= 0x1FFFFF) {//UTF-8 4byte
              binaryArray = binaryArray.concat(_toUTF8Binary(4, _tmpBinary));
          } else if (unicode >= 0x200000 && unicode <= 0x3FFFFFF) {//UTF-8 5byte
              binaryArray = binaryArray.concat(_toUTF8Binary(5, _tmpBinary));
          } else if (unicode >= 4000000 && unicode <= 0x7FFFFFFF) {//UTF-8 6byte
              binaryArray = binaryArray.concat(_toUTF8Binary(6, _tmpBinary));
          }
      }
      return binaryArray;
  };

  var _toUnicodeStr = function (binaryArray) {
      var unicode;
      var unicodeBinary = [];
      var str = "";
      for (var i = 0, len = binaryArray.length; i < len;) {
          if (binaryArray[i] == 0) {
              unicode = _toDecimal(binaryArray.slice(i, i + 8));
              str += String.fromCharCode(unicode);
              i += 8;
          } else {
              var sum = 0;
              while (i < len) {
                  if (binaryArray[i] == 1) {
                      ++sum;
                  } else {
                      break;
                  }
                  ++i;
              }
              unicodeBinary = unicodeBinary.concat(binaryArray.slice(i + 1, i + 8 - sum));
              i += 8 - sum;
              while (sum > 1) {
                  unicodeBinary = unicodeBinary.concat(binaryArray.slice(i + 2, i + 8));
                  i += 8;
                  --sum;
              }
              unicode = _toDecimal(unicodeBinary);
              str += String.fromCharCode(unicode);
              unicodeBinary = [];
          }
      }
      return str;
  };

  var _encode = function (str, url_safe) {
      var base64_Index = [];
      var binaryArray = _toBinaryArray(str);
      var dictionary = url_safe ? URLSAFE_BASE64_MAPPING : BASE64_MAPPING;

      var extra_Zero_Count = 0;
      for (var i = 0, len = binaryArray.length; i < len; i += 6) {
          var diff = (i + 6) - len;
          if (diff == 2) {
              extra_Zero_Count = 2;
          } else if (diff == 4) {
              extra_Zero_Count = 4;
          }
          var _tmpExtra_Zero_Count = extra_Zero_Count;
          while (--_tmpExtra_Zero_Count >= 0) {
              binaryArray.push(0);
          }
          base64_Index.push(_toDecimal(binaryArray.slice(i, i + 6)));
      }

      var base64 = '';
      for (var i = 0, len = base64_Index.length; i < len; ++i) {
          base64 += dictionary[base64_Index[i]];
      }

      for (var i = 0, len = extra_Zero_Count / 2; i < len; ++i) {
          base64 += '=';
      }
      return base64;
  };

  var _decode = function (_base64Str, url_safe) {
      var _len = _base64Str.length;
      var extra_Zero_Count = 0;
      var dictionary = url_safe ? URLSAFE_BASE64_MAPPING : BASE64_MAPPING;

      if (_base64Str.charAt(_len - 1) == '=') {
          if (_base64Str.charAt(_len - 2) == '=') {//两个等号说明补了4个0
              extra_Zero_Count = 4;
              _base64Str = _base64Str.substring(0, _len - 2);
          } else {//一个等号说明补了2个0
              extra_Zero_Count = 2;
              _base64Str = _base64Str.substring(0, _len - 1);
          }
      }

      var binaryArray = [];
      for (var i = 0, len = _base64Str.length; i < len; ++i) {
          var c = _base64Str.charAt(i);
          for (var j = 0, size = dictionary.length; j < size; ++j) {
              if (c == dictionary[j]) {
                  var _tmp = _toBinary(j);
                  /*不足6位的补0*/
                  var _tmpLen = _tmp.length;
                  if (6 - _tmpLen > 0) {
                      for (var k = 6 - _tmpLen; k > 0; --k) {
                          _tmp.unshift(0);
                      }
                  }
                  binaryArray = binaryArray.concat(_tmp);
                  break;
              }
          }
      }
      if (extra_Zero_Count > 0) {
          binaryArray = binaryArray.slice(0, binaryArray.length - extra_Zero_Count);
      }
      var str = _toUnicodeStr(binaryArray);
      return str;
  };

  var __BASE64 = {
      encode: function (str) {
          return _encode(str, false);
      },
      decode: function (base64Str) {
          return _decode(base64Str, false);
      },
      urlsafe_encode: function (str) {
          return _encode(str, true);
      },
      urlsafe_decode: function (base64Str) {
          return _decode(base64Str, true);
      }
  };

  return __BASE64;
}));